Shrimp eyes inspire optical tech

The abilty of peacock mantis shrimp to see circularly polarized light has inspired engineers to develop technology that may improve CDs and DVDs.

The future of CD and DVD technology may be found in the eyes of peacock mantis shrimp, an international team of engineers recently reported.

The shrimp are one of the few animals in the world that are able to see circularly polarized light, the type of light used to make 3-D movies.

Scientists believe this ability is related to sexual signaling, Roy Caldwell, a biologist at the University of California at Berkeley, told me on Friday.

"The strongest circularly polarized signal is certainly displayed during courtship and the assumption is it is important," he said.

The evidence for the ability to detect the circularly polarized light is based on Odontodactylus cultrifer, a relative of the peacock mantis shrimp (Odontodactylus scyllarus). The eyes of the peacock mantis shrimp are similar and easier to obtain for study.

Aklesh Lakhtakia, a professor of engineering science and mechanics at Pennsylvania State University, looked at these eyes in a bid to build a better waveplate.

Waveplates are optical devices that alter the polarization state of light that travel through them. This is important, Lakhtakia explained to me in an email on Friday, because "optical systems code different information on light of different polarization states."

"Polarization (or polarization state) is a property of light that human eyes do not appreciate but the eyes of many other animals do," he added.

"Waveplates are needed to either undo significant depolarization or to separate light of different polarization states. Of course, one also needs waveplates to filter light (generated by a source) of only a specific polarization to enter an optical device."

These devices are typically made from minerals such as quartz, calcite, or birefringent polymers. In some cases, to create the range and transparency required, two different materials are stacked or joined. Sometimes, though, this type of construction delaminates – it comes apart at the seams.

The method pioneered by Lakhtakia and colleagues with the National Taipei University of Technology, mimics the lens construction of peacock mantis shrimp.

These multilayered materials are suitable for waveplates in the visible light spectrum and cannot delaminate because they are manufactured as one piece.

The waveplate consists of two layers of nanorods; each layer deposited using different methods. One method produces a layer of needle-like nanorods that are parallel to each other and all slanted in the same direction. The second method produces parallel nanorods that are upright.

"The two separate layers are needed so that we can play off one against the other to achieve the desired polarization without significantly reducing transmittance over a broad range of frequencies," Lakhtakia said in a news release.

These layers are stacked together to make a waveplate. Eventually, this technology could lead to improved data storage devices and even higher high definition movies.

For now "we have just found a way to make an achromatic waveplate," Lakhtakia told me. The details are provided in the June 21 issue of Nature Communications. "Over time it will become part of optical systems," he added.